22 NEW YORK STATE MUSEUM 



The lower part of the Lockport is well shown at the crest of the 

 <ipper falls at Rochester, at the quarries on Goodman street and at 

 the culvert where the main line of the New York Central Railroad 

 crosses Allen creek. 



The change from the Rochester shale is a very gradual one. This 

 transition is accompanied by change in color of the rock as may be 

 observed from the Piatt street bridge. It will be observed that the 

 more massive layers which form the crest of the falls extend for a 

 distance at the top of the gorge on both sides of the river. The 

 admixture of the clayey material in these basal layers of the Lock- 

 port give it the chemical composition of a natural hydraulic 

 cement. These layers, however, have been used but little for 

 cement purposes. 



Some of the upper layers which form the crest of the falls contain 

 a number of crinoid stems, some of which measure i8 inches in 

 length. Farther west in Monroe county these crinoids become 

 more numerous and at Lockport they occur in such abundance 

 that the layer containing them has been designated the " crinoidal 

 limestone." 



The quarries on Goodman street show the transition beds to the 

 best advantage. Portions of the quarries extend down into the 

 Rochester shale. At the bottom of these quarries native sulfur is 

 found on some of the dark layers of the Rochester formation. A 

 fine sulfur spring was encountered in excavating in this formation 

 for the barge canal in the town of Greece. Some of the basal layers 

 of the Lockport are separated by thin layers of shale and are very 

 irregular in their stratification. Cross-bedding is very characteristic 

 of many of the lower portions which present an appearance of sand- 

 stone. It may be shown, however, that most of the grains consist 

 of small particles of dolomite. 



The two sections which show the Lockport dolomites to the best 

 advantage are along the Genesee river from the upper falls to the 

 rapids near South park and along Allen creek, 3 miles southeast 

 from Rochester. The former section is about in the center of the 

 city of Rochester and except where obstructed by dams, nearly the 

 entire section can be examined at times of low water. 



At Rochester the divisions of the Lockport dolomites, based 

 mainly on the lithologic character of the rock, were described by 

 Hall' as follows in descending order: 



iGeol. N. Y. 4th Dist. 1843. p. 87. 



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